1. Field of the Invention
The present invention relates to a device for detecting a location of an object using a pyroelectric infrared sensor.
2. Description of Related Art
A device for detecting a location of an infrared source using an infrared sensor recently has come into use for the purpose of prevention of crimes and calamities such as detection of an intruder or a fire or the like. As types of infrared sensors there are a quantum type using a compound semiconductor and a thermal type using a pyroelectric element or a thermister, etc. Since it is required for the quantum type infrared sensor to be cooled by liquid nitrogen and the like, the thermal type infrared sensor is used for the purpose of prevention of crimes and calamities and the like. In particular, the pyroelectric sensor has a higher sensitivity than other thermal-type sensors, and is therefore considered to be optimum for use as a position detector for a source of infrared radiation.
A pyroelectric sensor detects a temperature change of a sensor due to the variation of receiving quantity of infrared radiation as a voltage variation. Therefore, such a method is being employed in which infrared radiation interrupted by a rotating optical chopper and the like is irradiated to an arranged pyroelectric sensor array and in which outputs of respective sensors are compared after impedance conversion and a.c. amplification of outputs of these sensors, thereby to detect a position of a source of infrared radiation.
When the resolution of positional detection is elevated in said conventional example, the number of arranged pyroelectric elements is increased. Thus, the number of processing circuits for impedance conversion and a.c. amplification and the like for the pyroelectric elements is increased accordingly. In addition, when the number of pyroelectric elements is increased, the number of wirings between respective pyroelectric elements and processing circuits is also increased, thereby causing the distribution of wirings to become complicated. In particular, when an arrangement is made in two dimensions, the number of elements and the number of processing circuits are increased in proportion to the square of the resolution, and wiring between pyroelectric elements and processing circuits becomes difficult.
Furthermore, when picture image information is to be processed with a microprocessor and the like, it is required to read signals from respective pyroelectric elements after converting them into time series signals, and a circuit for scanning all the pyroelectric elements successively has to be added.
As described above, the device becomes large in size and the production cost thereof is also increased at the same time in a conventional example.